The present invention relates to a weft reservoir for fluid-jet looms, and more particularly relates to improvement in construction of a weft reservoir on which weft is wound for reservation about a stationary drum-type weft reserving section by operation of a yarn guide rotating around the weft reserving section.
On a weft reservoir of this type in general, the length of weft for one pick is reserved on the weft reserving section in the form of a number of continuous windings at prescribed intervals and the reserved weft is sequentially transferred in the axial direction of the weft reserving section, i.e. the delivery direction of weft.
The length of weft for one pick varies depending on the width of the cloth to be woven. In order to change the length of weft for one pick, the amount of weft to be wound on the weft reserving section has to be changed. To this end, it is theoretically thinkable to change the number of windings on the drum-type weft reservoir. In practice, however, change in number of windings often makes it infeasible to obtain a correct length of weft for one pick. In order to avoid this inconvenience, it is also thinkable, in combination with change in number of windings, to change the diameter of the weft reserving section in order to assure a correct length of weft for one pick.
For example, the weft reservoir disclosed in the Japanese Patent Opening No. 55-2595 based on the Dutch Application No. 7806469 suffices this requirement to an appreciable extent. In the case of this previous weft reservoir, its weft reserving section is comprised of two different parts combined in an axial alignment, i.e. the first part fixed to the drive shaft and a fixed diameter and the second part having adjustable in diameter. A yarn guide is driven for rotation around the weft reserving section for weft reservation. The first part is accompanied with a weft transfer mechanism which sequentially transfers winds of weft on the first part in the axial delivery direction. By adjusting the diameter of the second section, the peripheral length of the weft reserving section can be varied as desired in order to obtain a correct length of weft for one pick in accordance with the width of the cloth to be woven.
This previous weft reservoir, however, is still accompanied with an operational trouble caused by the manner of change in diameter of the second section. The weft is delivered from the weft reservoir by fluid ejection of the main nozzle after the weft transfer mechanism has disappeared under the peripheral surface of the first section. Since the peripheral surface of the weft reserving section is in general rendered very smooth in order to minimize resistance against weft delivery. This low resistance, however, makes the unwinding of weft from the first part quicker than the delivery speed by the main nozzle thereby causing extremely large ballooning of the weft under delivery.
As described already, the weft winding section now in question is made of the first and second parts both coupled to the common drive shaft. In order to adjust the amount of weft to be wound on the weft reserving section, the diameter of the second section only is changed. Since the change in diameter is performed in an eccentric fashion, the second part assumes an oblong transverse cross sectional profile after this change in diameter which inevitably causes difference in distance between peripheral points on the weft reserving section and a main nozzle side yarn guide eye. This produces a gap between the axis of weft baloon and the axis of the main nozzle side yarn guide eye.
This gap and the above-described low resistance against weft delivery further unstable weft balooning. Such unstable weft balooning naturally causes undesirable fluctuation of weft delivery tension and tends to eventuate in unstable weft picking.